The document discovered among a file of 18th century papers. It is one of only 26 surviving copies

It was found by chance by an American antiquarian bookseller
carrying out unrelated research in the National Archives in Kew, West
London.

The manuscript was hidden among correspondence from U.S.
colonists that had been intercepted by the British in the 18th century.

The Declaration, which helped establish the guiding principles
of modern democracy, was written mainly by U.S. Founding Father Thomas
Jefferson and is described by historians as 'America's birth
certificate'.

It includes the then extraordinary assertion: 'We hold these
truths to be self-evident, that all men are created equal,' which paved
the way for the French Revolution 13 years later.

It was signed by 56 delegates from the 13 American colonies that were at war with Britain.

The 200 first copies were made by printer John Dunlap that night and distributed throughout the colonies the following morning to be read aloud to the colonists and their militia.

It is not certain how the newly discovered copy came into British hands, but it is likely to have been captured by the Royal Navy during the American Revolutionary War which continued for seven years after the Declaration of Independence was signed.

The last discovery of a Dunlap print was at a flea market in 1989, and it sold at auction in 2000 for £4.94million.